This invention pertains to methods and apparatus for moving and handling sheet media, including plastic film and paper. More specifically, the invention pertains to methods and apparatus to compensate for performance loss in media-contacting surfaces in imaging devices, such as printers and copiers, due to wear of such surfaces.
Many various types of prior art imaging devices are known. Imaging devices are employed to produce visual images on sheets of media. Media is typically in the form of paper, but can also be in other forms such as plastic transparencies. Imaging devices include printers, copiers, facsimile machines, and the like. That is, imaging devices include any type of device which is configured to produce a visual image on a sheet of media.
Prior art imaging devices often employ feed mechanisms which are configured to feed, or move, sheets of media through the imaging device. For example, a feed mechanism is often employed to pick sheets of media, one-at-a-time, from a stack of media in order to feed individual sheets of media into an imaging device. The feed mechanism, or other feed mechanisms, can be employed to feed the individual sheets of media through the imaging device as images are applied to the sheets of media, or as other such processes are performed on the sheets of media.
Feed mechanisms generally comprise rollers or the like for moving the sheets of media through the imaging device. The feed mechanisms also generally comprise various drive components which are configured to drive the rollers so as to impart rotation thereto. Feed mechanisms, then, include any components which are configured to facilitate the movement of sheets of media through the imaging device.
Feed mechanisms typically comprise gripping surfaces which are configured to contact and grip the sheets of media in order to facilitate the movement of the sheets of media through the imaging device. The gripping surfaces are often defined on the outer cylindrical surfaces of the rollers which make up the feed mechanisms. An example of a gripping surface is a relatively soft rubber coating on the roller. The rubber coating is preferably sufficiently soft so as to facilitate a relatively high static frictional force between the roller and the sheets of media. However, the rubber coating is also preferably not so soft as to leave a visible deposit or marking on the sheets of media as they are moved into and through the imaging device by the roller, or rollers.
As the prior art imaging devices are operated, the gripping surfaces tend to experience wear. This wear can be due to abrasion and the like from repeated contact with sheets of media as the media is moved by the gripping surfaces. The wear experienced by the gripping surfaces can cause problems with the operation of the feed mechanisms. In particular, the wear of the gripping surfaces can cause slippage of the gripping surfaces relative to the sheets of media. Such slippage and the like can, in turn, result in media jams and mis-feeds, as well as multiple media picks and the like. What is needed then, are methods and apparatus for feeding media which achieve the benefits to be derived from similar prior art devices, but which avoid the shortcomings and detriments individually associated therewith.
The invention includes methods and apparatus for feeding, or moving, media along a media path. The apparatus can be employed, for example, in conjunction with an imaging device to move media along a media path which passes through the imaging device. A gripping surface is employed to contact, and thereby move, the media along the media path. The invention further includes methods and apparatus for increasing the force with which a gripping surface contacts the media in order to compensate for wear experienced by the gripping surface.
In accordance with one embodiment of the present invention, an apparatus includes a gripping surface and a wear compensator configured to selectively increase the force with which the gripping surface contacts the media.
In accordance with another embodiment of the present invention, a method includes providing a rotatable feed roller in an imaging device, the roller having a gripping surface defined thereon. The gripping surface is configured to contact and grip the media as the roller feeds sheets of media into and through the imaging device. The method also includes measuring the rotation of the feed roller and increasing the force with which the gripping surface contacts the media in response to measuring rotation of the feed roller.
In accordance with yet another embodiment of the present invention, a method includes providing a gripping surface defined on a feed roller or the like which can be used in an imaging device or the like. The imaging device is configured to generate an image on a sheet of media. In the method, the media is contacted by the gripping surface. A variable is measured and the force with which the gripping surface contacts the media is increased as a function of the measured variable. The measured variable can be, for example, a number of rotations of a feed roller, or a number of sheets of media which pass a given point.